COFFEE, TEA, AND CHOCOLATE. 



189 



should be conducted slowly and gently, until the grains assume a chestnut-brown color. 

 During this process, the grains are considerably swollen, but they lose from sixteen to 

 seventeen per cent, in weight. A peculiar aromatic principle is also developed by roasting. 

 If the torrification be pushed too far, much of the agreeable flavor is lost, and an acrid 

 empyreumatic principle is produced. An infusion of fifteen hundred grains of roasted 

 and ground coffee in about a quart of boiling water, the infusion made by simple per- 

 colation, contains about three hundred grains of the soluble principles. According to 

 Payen, this contains about one hundred and forty grains of nitrogenized matters and 

 one hundred and fifty-three grains of fatty, saccharine, and saline substances. There is 

 every reason to suppose that that these principles are assimilated; and an infusion of 

 coffee, with milk and sugar, presents, therefore, a considerable variety and quantity of 

 alimentary matter. The peculiar stimulant effects of coffee are probably due to the 

 caffeine and volatile oil. 



In the countries where coffee is grown, the leaves of the shrub, roasted and made into 

 an infusion, are quite commonly used. Their effects upon the system are similar to those 

 of coffee, and it is said that the natives prefer the leaves to the berry. 



Tea. 



An infusion of the dried and prepared leaves of the tea-plant is perhaps as common a 

 beverage as coffee, and, taking into consideration its immense consumption in China and 

 Japan, it is actually used by a greater number of persons. Its effects upon the system are 

 similar to those of coffee, but are generally not so marked. Ordinary tea, taken in 

 moderate quantity, like coffee, relieves fatigue and increases mental activity, but does not 

 usually induce such persistent wakefulness. 



It is unnecessary to describe all the varieties of tea in common use. There are, how- 

 ever, certain varieties, called green teas, which present important differences, as regards 

 composition and physiological effects, from the black teas, which are more commonly 

 used. The following is a comparative analysis of these two varieties by Mulder: 



Composition of Tea. 



Both tea and coffee possess peculiar organic principles. The active principle of tea is 

 called theine, and the active principle of coffee, caffeine. As they are supposed to be 

 particularly active in producing the peculiar effects upon the nervous system which are 

 characteristic of both tea and coffee, there is good reason to suppose that they are nearly 

 identical in their physiological effects. Theine (or caffeine) exists in greater proportion 

 in tea than in coffee ; but, as a rule, much more soluble matter is employed in the prepara- 

 tion of coffee, which may account for its more marked effects upon the system. 



